Applicants, first, wish to incorporate by reference U.S. Pat. No. 3,970,404 issued on July 20, 1976 to co-inventor Angelo W. Benedetti. This patent discloses a method of reconstructing asphalt pavement wherein the pavement is heated with radiant energy until the pavement surface achieves a temperature within the range of 225.degree. F. to about 325.degree. F. to thereby soften the pavement surface. Thereafter, the application of radiant energy is discontinued to permit the heat applied to be conducted deeper into the asphalt pavement without overheating the surface to thereby soften the asphalt pavement to an incremental depth. Thereafter, the previously heated surface is reexposed to a source of radiant energy to elevate its energy to a value not exceeding about 325.degree. F. to thereby further soften the surface thereof. Thereafter, the application of radiant energy is discontinued to permit the heat last applied to be conducted deeper into the asphalt pavement without overheating the surface, thereby further softening the asphalt pavement to a further incremental depth.
Thereafter, the thereby softened asphalt is scarified to a depth not exceeding the further incremental depth so as to eliminate any surface cracks or discontinuities therein. Thereafter, a leveling operation is accomplished through the use of a screed to level the pavement, whereupon rolling, compacting and rejuvenation steps are thereafter applied.
The method described in U.S. Pat. No. 3,970,404 and basically explained above was quite effective in recycling an asphalt surface, however, when the process described in U.S. Pat. No. 3,970,404 was completed, the pavement was filled with voids. In the paving industry, voids are defined as areas where there is no sand or asphalt and water may collect in these voids whereupon the subsequent intrusion into the pavement structure acts, over a period of time, to delaminate the pavement through repeated freezing and thawing as well as dilution of the asphalt mix through the addition of water thereto.
In the method described in U.S. Pat. No. 3,970,404, the top layer of the original asphalt surface, to a depth of approximately one inch was recycled. Due to the fact that the above-described voids were always created when an asphalt surface was recycled through the use of that method, after the leveling step thereof, as shown in the sole figure therein, an overlay had to be applied over the recycled surface so that the resulting road surface would be smooth and durable. Experience showed that the overlay had to be at least 5/8 inch thick over the recycled asphalt. This was because the aggregate which comprises one of the constituent parts of the asphalt mix includes stones which are up to 5/8 inch in diameter and with these stones utilized in the aggregate, the thickness of the new layer could not be reduced below the stone diameter otherwise bumps and discontinuities would result in the overlay. On the other hand, it was discovered that if the overlay was made up of sand aggregate, the overlay did not have sufficient strength to maintain continuity over the road surface over any extended period of time.
Some paving contractors tried to solve the problem of voids by filling the voids with sand and mineral fillers but such methods were quite time consuming and expensive and did not guarantee that the voids would be eliminated. In this regard, in filling the voids with sand and mineral fillers, if the resulting surface was not completely smooth, this resulted in additional voids being formed by the surface structure of the fillers. Thus, where a plurality of voids had been added by the use of fillers, the pavement became slick and slippery which caused the road surface to become dangerous.
Other problems resulted from the fact that an additional overlay of at least 5/8 inch had to be applied over the repaved asphalt surface. Firstly, due to the increase in the actual level of the surface of the road which results from providing such a thick overlay, all of the man-holes, water boxes and inlet basins of a road had to be raised. In any paving contract, raising these structures normally costs approximately 20% of the total contract price. Thus, stated another way, the fact that a thick overlay had to be applied resulted in a vast increase in the cost of repaving due to the fact that one important contract item consisted of the labor charges for raising all of the road structures which would otherwise be covered by the overlay.
Furthermore, due to the thickness of the overlay, paving contractors had to be quite careful not to disturb the drainage which had been built into the original road surface due to its angle, and utility castings had to be adjusted to a new height.
In another aspect, in order to add a 5/8 inch overlay to an existing road surface, a great deal of energy resources must be expanded. It is well known by those skilled in the paving industry that asphalt includes as a constituent part petroleum. In fact, for every ton of asphalt which includes stone, sand and liquid, approximately 120 pounds of the ton consists of petroleum. Applicants have discovered that one ton of asphalt spread approximately 1 inch thick covers approximately 150 square feet. Thus, a roadway 1 mile long and 10 feet wide paved 1 inch thick would require approximately 350 tons of asphalt of which approximately 21 tons would consist of petroleum. As it must be understood, in order to apply an overlay of asphalt to a road surface, the road surface and the overlay must be heated as described above to a temperature of at least 225.degree. F. and the thicker the overlay the more energy is required to elevate the asphalt to the appropriate temperature. Furthermore, large expenditures of energy resources are required to mine the stone, wash it, truck it and heat it, and the same applies to the sand which is utilized.
Further, applicants are aware of the U.S. Pat. No. 4,643,360 to van der Lely et al. which discloses a spreader in several embodiments. The embodiments include devices including plural spinners, and different embodiments of hopper and discharge details. In the embodiment shown in particular in FIGS. 1 and 3, the discharge port on the hopper is conically shaped with a protruding floor having a radially disposed cavity and two radially disposed distribution vanes which are fixed in position. Two openings, 29 and 30, are formed on the conical collar wall which lead to a distribution plate which is upwardly angled and has 4 distribution paddles which are curved both in the vertical and horizontal direction. The manner of adjustment of the openings 29 and 30 is such that as the openings are adjusted, their axis of symmetry shifts circumferentially about the distribution device. In the embodiment shown in FIGS. 7-10, the outlet port on the spreader is a cylindrical collar, however, the distribution device comprises a conical device having curved vanes which extend outwardly from the central axis of rotation of the device and which are nonadjustable. The outer distribution plate of the spreader disclosed in FIGS. 7-10 appears to be the same as that which is disclosed in FIGS. 1-6.
Several significant differences exist between the teachings of the van der Lely et al. patent and the teachings of the present invention. Firstly, each of the embodiments of van der Lely et al. include structure in their inner chambers which would not work in the environment of spreading of asphalt materials. In the embodiment best seen in FIG. 3, the conical nature of the distribution collar and the fact that the outlet openings are formed on this conical member cause a vertical component of discharge which results in bouncing of the material on the distribution plate 43 which is quite disadvantageous when one is spreading a heavy material such as asphalt. Furthermore, since the distribution vanes in the inner chamber designated by the reference numeral 57 and best seen in FIG. 2, extend directly radially outwardly from the axis 13 of rotation of the device, very little mechanical advantage is obtained in the central portions thereof and the likelihood exists that asphalt materials would cling to the central portions of the vanes 57 and build-up causing clogging of the device. The same effect would happen on the outlets 29 and 30 because even though their combined area may equal the total area of the single distribution port of the present invention, the fact that the total area is comprised of two smaller openings would cause additionally clumping and clotting of the openings with the asphalt material as it caught in the region between the openings 29 and 30 and accumulated and hardened.
On the other hand, concerning the embodiment of FIGS. 7-10, the conical nature of the distribution device causes a restricted area to be formed adjacent to the outlets which would cause further clotting of the material and clogging of the distribution path. In a further aspect, with reference back to FIGS. 1 and 3, the region between the plate 40 and the conical collar 25 is an area where if used to distribute asphalt, the asphalt would accumulate, cool and harden thus causing disruption of the proper operation of the device. Furthermore, common to both embodiments of van der Lely et al., is the structure of the paddles 53. Firstly, they are nonadjustable and their curvature in the horizontal and vertical directions as well as their up-lifted nature best seen in FIG. 3 are all designed to enable the throwing of large quantities of material a great distance. In this regard the patent discloses throwing material as far as 25 meters. Contrary to this teaching, in the present invention, it is specifically intended that small quantities of material be distributed over a radius of no more than 3 to 4 feet from each spinner with even distribution in that area. With asphalt material being composed of aggregate of varying sizes, if it were to be thrown with distribution paddles such as those designated by the reference numeral 53 in van der Lely et al., the result would be a quite uneven distribution as aggregate of different sizes would be thrown non-uniform distances from the distribution plate thereof.
In contrast to these teachings of van der Lely et al., the present invention includes inner and outer paddles each of which is adjustable for angle and each of which consists of a straight elongated member to maximize the ability to move heavy material outwardly while minimizing the ability to throw the material a great distance. In this way, a uniform pattern of distribution is possible through the teachings of the present invention.
In a further aspect, concerning the teachings of van der Lely et al., as stated above, when the openings 29 and 30 are adjusted as to their size, the line of symmetry about which the openings extend is circumferentially moved. As opposed to this, in the present invention as will be discussed in greater detail hereinafter, it is crucial that the axis of symmetry about which the opening extends is maintained in the same position approximately 45.degree. from the longitudinal axis of the machine. Applicants have found that through placement of the opening at that region, more uniform distribution of material throughout the swath of pavement being repaved and recycled occurs.
Furthermore, in the present invention, adjustments of the thickness of the material distributed may be accomplished in six ways, through adjustment of the size of the distribution opening, through adjustments of the angle of attack of the internal paddles, through adjustments of the angle of attack of the outer paddles, through changes in the speed of movement of the device itself, through adjustments in speed of rotation of the spinners, and through any combination of adjustments of the above. Since the van der Lely device depends for its operation on interconnection with the power take-off shaft of the supporting tractor, as the speed of the supporting tractor increases, so does the speed of the spinners proportionally. Thus, the only way to adjust the speed of rotation of the spinners of the van der Lely device is through changes in the speed of forward movement of the device. This is completely different from the teachings of the present invention.
Furthermore, van der Lely et al. disclose the ability to adjust the position of the ports 29 and 30 about the rotary axis 13 and disclose structure for performing this function. This indicates that in the van der Lely device there is no criticality in the particular position of the ports 29 and 30 about the rotation axis 13. This is to be contrasted with the teachings of the present invention where there is extreme criticality in the particular position of the single outlet port thereof. Furthermore, in the present invention, it is contemplated that the spinners rotate in the range of approximately 10 to 50 revolutions per minute. This is extremely slow rotation as compared to what may be inferred from the teachings of van der Lely et al. since the van der Lely spinners would have to rotate at much higher speeds in order to throw any material 25 meters as is disclosed therein.
Finally, the cylindrical nature of the outlet collar of the present invention combined with the flat bottom of the chamber formed thereby allow large aggregate materials to be dispensed therefrom without clogging or clumping of the materials and thereby disrupting the operation of the machine. This is contrasted with the teachings of van der Lely et al. which show structure which if used in the environment of spreading of asphalt aggregate materials would cause clumping, clogging and quite definite impediment of the smooth flow and distribution of materials from the device.
Accordingly, for the reasons set forth hereinabove, applicants believe that the present invention clearly patentably distinguishes in all respects from the teachings of van der Lely et al.
Accordingly, in light of the above-described problems in the asphalt paving industry, including those discussed with reference to U.S. Pat. No. 4,643,360, a need has developed for a machine and method which could be utilized to apply an extremely thin overlay over a repaved asphalt surface so that all voids could be filled while saving energy over prior methods, while eliminating the need for adjustments to man-holes, water boxes and inlet basins.